1. Field of the Invention
This invention relates to a rigid thermal sleeve for a gun barrel which has a reduced thermal signature and a reduced radar cross-section, and in particular to a rigid thermal sleeve for a tank gun barrel.
2. Discussion of Prior Art
In certain weather conditions a gun barrel can be heated or cooled on one side more than the other, for example, when the gun barrel is in direct sun light or when wind and rain is blowing from a particular direction. The uneven heating of the gun barrel can cause it to deform and so reduce the accuracy of the gun. This problem has conventionally been solved by thermally insulating the gun barrel from its surroundings, for example, by wrapping blankets of asbestos and/or fibre glass around the gun barrel.
In European Patent No. 0,183,432 a rigid thermal sleeve for a tank gun is disclosed which when mounted on the gun barrel of the tank defines an annular gap between the sleeve and the gun barrel. The sleeve is made of an honeycomb material sandwiched between outer and inner rigid envelopes of thermally insulating material. Such an arrangement effectively insulates the gun barrel from its surroundings and has the additional advantage that it can be easily removed from the gun barrel and so can be reused on replacement of the gun barrel.
However, rigid thermal sleeves of the type disclosed in EP 0,183,432 have a distinctive thermal signature, because of their distinctive shape and generally uniform temperature. Due to their insulating nature heat inputs to the surface of the thermal sleeve are not conducted into the bulk material of the sleeve leading to temperature differences between the thermal sleeve and its surroundings. The distinctive thermal signature of such thermal sleeves makes the tank on which it is used vulnerable to detection by infra-red thermal imaging equipment.